Installation Guide

8 CONCRETE — Floors, Interior - Ceramic or Stone Tile
Every substrate presents unique challenges
CONCRETE
Floors, Interior - Ceramic or Stone Tile
DH-C-TS-17
There are various challenges associated with the installation of hard surface coverings on concrete substrates.To begin, the coefficient of thermal
expansion of concrete is close to twice that of ceramic tile. Additionally, tile contractors are often expected to install tile over young concrete
(concrete cured less than 28 days). However, rigid surface coverings installed over young concrete are susceptible to damage as a result of
shrinkage during curing. Pre-stressed/post-tensioned concrete slabs are also commonplace in today’s construction environment. Although pre-
stressing is used to help control deflections in concrete structures, these slabs are still subject to deformations caused by changes in moisture,
temperature, and loading. Many concrete slabs on or below grade are subject to moisture migration, which can be problematic. Furthermore,
these structures experience the same deformations as stated above.
DITRA-HEAT’s uncoupling function protects the ceramic or stone tile covering by neutralizing the differential movement stresses
between the concrete substrate and the tile, thus eliminating the major cause of cracking and delaminating of the tiled surface.
DITRA-HEAT’s waterproofing ability not only protects the substrate from harmful substances, it also slows the drying of fresh
concrete, which reduces the chances of cracking and curling of the slab.
The configuration of the DITRA-HEAT matting provides free space to accommodate vapor emissions from the concrete slab.
This allows the installation of DITRA-HEAT and the tile covering as soon as the slab can be walked upon. Vapor management is
also essential for slabs subject to moisture migration.
Since DITRA-HEAT is virtually incompressible within the tile assembly, the advantages of uncoupling are achieved without
sacrificing point load distribution capabilities.
By addressing all of the challenges associated with today’s fast construction methods, DITRA-HEAT provides a durable installation system for
ceramic and stone tile over concrete substrates.
DITRA-HEAT combines the flexibility of loose heating cables with the ease of installation of mat systems. Cables can be placed wherever heat is
desired, without creating height differences in the floor. Self-leveling compounds are not required to encapsulate the cables, significantly reducing
installation time and effort compared to uncoupling membranes over other electric floor warming systems. DITRA-HEAT-TB features an integrated
thermal break to reduce heat loss to concrete substrates and improve floor warming response times.
Concrete subfloor
Areas of Application
over any structurally sound and even concrete
subfloor
young concrete (concrete cured less than 28 days)
on or below grade concrete subject to moisture
migration
post-tensioned or pre-stressed concrete
cracked concrete
Limitations
minimum 2" x 2" (50 mm x 50 mm) tile
concrete slabs subject to moisture migration
must have all seams in DITRA-HEAT and
DITRA-HEAT-TB sealed with KERDI-BAND
using unmodified thin-set mortar
any cracks in concrete subfloor must exhibit
in-plane movement only; thin-set tile assemblies,
including those incorporating DITRA-HEAT or
DITRA-HEAT-TB, cannot accommodate
differential vertical displacement
Requirements
slab to be structurally sound
slab to be free of waxy or oily films and curing
compounds (when present, mechanical
scarifying is necessary)
the installation of DITRA-HEAT or DITRA-HEAT-
TB and tile can begin as soon as the slab can be
walked upon
slab to be free of standing water
Substrate Preparation
any leveling of the subfloor must be done prior
to installing DITRA-HEAT and DITRA-HEAT-TB
Movement Joints
DITRA-HEAT and DITRA-HEAT-TB do not
eliminate the need for movement joints, including
perimeter joints, within the tiled surface. Movement
joints must be installed in accordance with industry
standards and norms; see page 11 of this
Handbook, TCNA EJ171, and TTMAC 301 MJ
Setting and Grouting Materials
unmodified thin-set mortar – ANSI A118.1
grout – ANSI A118.3, A118.6, A118.7, A118.8
Setting and Grouting Specifications
tile – ANSI A108.5
grout – ANSI A108.6, A108.9, A108.10
Other Considerations
where a waterproof floor is required, all
DITRA-HEAT and DITRA-HEAT-TB seams and
floor/wall transitions must be sealed with KERDI-
BAND using unmodified thin-set mortar; see page
10
certain moisture-sensitive stones, e.g., green
marble, or resin-backed tiles may require special
setting materials. Consult stone supplier and
Schluter
®
-Systems for more information
consider the use of DITRA-HEAT-TB to improve
the response time of DITRA-HEAT in applications
over concrete. See page 24 for more information.
Ceramic, porcelain
or stone tile
Unmodified thin-set mortar
DITRA-HEAT
or DITRA-HEAT-TB
uncoupling membrane
and heating cables
Unmodified
thin-set mortar
Concrete